Introduction

Emotion is one of the most controversial topics in psychology,
a source of intense discussion and disagreement from
the earliest philosophers and other thinkers to the present day.
Most psychologists can probably agree on a description of emotion,
e.g., what phenomena to include in a discussion of emotion.
The enumeration of these parts of emotion are called the "components of emotion" here.
These components are distinguished on the basis of physiological or psychological factors and include emotion faces, emotion elicitors, and emotion neural processes.

Components of Emotion

Common representationof angry emotion experience:"steamed up" with hot glowingeyes, and uncontrolled
appearance. Is it the same across
people?

Interpersonal aggression in the
form of instrumental behaviors
produced by skeletal muscles is
often a concomitant of anger.

A bright idea can bring a pleasant
emotion, or pleasant emotions
can foster bright ideas.

The component that seems to be the core of common sense approaches to emotion,
the one that most people have in mind when talking about human emotions, is the feeling component, i.e., the passion or sensation of emotion. For
example, people generally agree that the state of mind during anger is
different from that when one is happy. This component is also one of the
most contentious in scientific discussions of emotion, raising many
questions such as:

to what extent are such feelings, especially the claimed differences in quality, based on real physical differences?

is the feeling quality of a particular emotion shared among people?

what is the nature of the differences in quality among emotions?

what underlies or produces these feelings?

what importance or function do such feelings have?

Another obvious descriptive component of emotion is the set of behaviors that may be performed and observed in conjunction
with an emotion.
These behaviors are produced by the striated muscular system and are of two general types:
gross behaviors of the body effected by the skeletal muscles and the so-called emotion expressions.
These categories shade into each other because any behavior can be interpreted as expressing emotion.
The gross body behaviors may have no apparent adaptive value,
e.g., wringing and rubbing the hands or tapping a foot,
or they may be directed towards a goal,
e.g., striking something or running away.
In the field of animal behavior, discovering the adaptive function and organization of behaviors in situations analogous to human emotion, and speculating on the evolutionary patterns of these behaviors is an established endeavor. This emphasis has not typically been given to the study of human emotions by psychologists. The facial and bodily behaviors called "emotion expressions" are indicators of emotion,
as opposed to effecting some action or achieving some goal. These expressions can
differentiate one emotion from another.
The most widely discussed and investigated emotion expressions are the emotion faces (see the examples of emotional expressions).

Adrenalin is a secretion that affects many organs
and
may contribute to the felt quality of emotion.

A less obvious component of emotion is the set of internal bodily changes
caused by the smooth muscles and glands.
Chemicals secreted by the body's various glands are activated during emotion
and spread to other parts of the body, usually by the blood, to act in diverse
ways on the nervous system and other organs.
Smooth muscles of the digestive system, circulatory system, and other bodily components
can shift from their typical level or type of operation during emotion under the effects of chemical and neural action.
This component includes some behaviors that can be observed,
such as the constriction or dilation of the iris of the eye,
possibly piloerection, and sweating, blanching, and flushing of the skin, and other responses that are relatively hidden, such as heart rate, stomach activity, and saliva production.

Computers often elicit frustration and anger

Another less observable component in emotion consists of the ideation, imagery, and thoughts that occur during emotion.
These aspects of emotion are also cognitive activities, and can both give rise to an emotional event and be affected by it, e.g., thinking about a lost pet may evoke feelings of sadness, which may in turn evoke memories of a romance now finished.
Since thoughts and other cognitions, like feelings, cannot be directly observed and are hard to measure,
there is less understanding of how they fit into the emotion picture than other components.

The circumstances that give rise to emotions comprise another component,
called the "elicitors" of emotion.
These elicitors might be internal or external to the organism, e.g., a frightening pain in one's chest or a frightening dog at one's heels.
Some events seem to activate similar emotion in people of all cultures, for example, the death of one's own child typically elicits sadness. Other things, such as what foods are relished or rejected with disgust, vary widely according to acculturation.

Finally, the neural processes that underlie much of the preceding activities can be considered a component of the emotion process, especially how the neurons and their emotional concomitants are organized centrally in the brain. Many contemporary research studies, and thus a lot of the research money, is focussed on anatomical and functional aspects of brain activity in regard to emotion.

Theories of Emotion

Beyond the descriptive approach to emotion, there are theories of emotion, which attempt to specify the interrelationships among components as described above and the causes, sources, and functions of emotional responses. Disagreement characterizes the intellectual climate surrounding emotion theories, but there are several works in print that summarize these approaches for the interested reader. The Theories of Emotion page of this section summarizes some of the most important theoretical statements on emotion that emphasize the role of the face.

Expression of Emotion

Emotion expression is another area of controversy, but at the descriptive level, some behaviors tend to occur with other components of emotion, and seem to reveal the quality of the emotion to an observer. The Emotion Expressions page of this section discusses the relations between emotion and facial expression.